This spring, a federal agency announced that Asian carp eggs had been discovered in Pool 9 of the Mississippi River, about 250 miles farther north than reproducing populations of these carp were thought to have existed.
The finding stunned fisheries researchers and managers, and added urgency to plans already in place to stop the carp from swimming further upstream and establishing footholds in the Mississippi as far north as the Twin Cities, and in the Minnesota and St. Croix rivers.
Federal fisheries managers had concluded by visual inspection that the eggs were those of either silver or bighead carp.
Now the U.S. Geological Survey says the eggs are not those of any of the four species of Asian carp that are plaguing U.S. waters: bighead, silver, black or grass.
The mistaken discovery had prompted University of Minnesota researcher Peter Sorensen — shown with other researchers in the photo above at their U labraotory — to accelerate plans to place speakers (technically, transducers) on the downriver side of the downriver lock doors of Lock and Dam 8 near Genoa, Wis.
The speakers cost about $7,000 apiece, require about $2,000 a year in electricity to operate and would be attached to the lock by divers.
Sorensen said Tuesday that installation of the speakers, which likely will transmit motorboat sounds, is going ahead, regardless of the egg identification mistake, noting that rogue specimens of Asian carp have been found as far north as the St. Croix River since 1997.
Stopping upstream migrations of Asian carp further south on the Mississippi is also the only way to protect the Minnesota River, as well as the St. Croix, from reproducing infestations of these fish, Sorensen has noted.
Sorensen doesn't think the speakers will thwart 100 percent of Asian carp swimming upstream. But he believes the concept will be effective, and if so, additional speakers might be added in the future at Lock and Dam 5 and possibly Lock and Dam 3.
Sorensen and other researchers at the U also plan to use the school's supercomputer beginning this summer to simulate flow adjustments on Mississippi River dams that might further inhibit upstream movement of Asian carp.
The U.S. Corps of Engineers is cooperating in these and other efforts, Sorensen said.
The speaker project is being funded largely by lottery money overseen by the Legislative-Citizen Commission on Minnesota Resources (LCCMR), together with some private funds.